Compilation Failure on GCC < 10.2 and Clang < 10.0.0 for undefined AVX512VL and AVX512F intrinsics
### Summary
Eigen 5.0.1 will fail to compile on gcc versions less than 10.2 if the user uses a `Eigen::Matrix<int, -1, -1>` on a system with AVX512VL (gcc <= 9.5) or AVX512F (gcc <= 10.2) capabilities.
Similarly, Eigen 5.0.1 will fail to compile with clang < 10.0.0 for a missing AVX512F intrinsic `_mm512_cvtsi512_si32`
See the example godbolt below
### Environment
<!-- Please provide your development environment. -->
- **Operating System** : Linux
- **Architecture** : x64
- **Eigen Version** : 5.0.1
- **Compiler Version** : <= gcc-10.1
- **Compile Flags** : -O3 -march=native
- **Vector Extension** : avx512f avx512vl
### Minimal Example
#### GCC Example
With gcc < 10.1 and `-mavx512f -mavx512vl -mfma` flags
```cpp
#include <Eigen/Dense>
int main() {
using mat_t = Eigen::Matrix<unsigned int, -1, -1>;
mat_t A = mat_t::Random(10, 10);
}
```
[https://godbolt.org/z/3sonxqP1o](https://godbolt.org/z/aTPT8rvbd)
Produces the following compile errors
```
In file included from /opt/compiler-explorer/libs/eigen/vtrunk/Eigen/Core:222,
from /opt/compiler-explorer/libs/eigen/vtrunk/Eigen/Dense:1,
from <source>:1:
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h: In function 'Packet Eigen::internal::ploadu(const typename Eigen::internal::unpacket_traits<T>::type*) [with Packet = __vector(8) long long int; typename Eigen::internal::unpacket_traits<T>::type = int]':
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h:1036:37: error: '_mm512_loadu_epi32' was not declared in this scope; did you mean '_mm512_load_epi32'?
1036 | EIGEN_DEBUG_UNALIGNED_LOAD return _mm512_loadu_epi32(from);
| ^~~~~~~~~~~~~~~~~~
| _mm512_load_epi32
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h: In function 'Packet Eigen::internal::ploadu(const typename Eigen::internal::unpacket_traits<T>::type*) [with Packet = Eigen::internal::eigen_packet_wrapper<__vector(8) long long int, 1>; typename Eigen::internal::unpacket_traits<T>::type = long int]':
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h:1040:37: error: '_mm512_loadu_epi64' was not declared in this scope; did you mean '_mm512_load_epi64'?
1040 | EIGEN_DEBUG_UNALIGNED_LOAD return _mm512_loadu_epi64(from);
| ^~~~~~~~~~~~~~~~~~
| _mm512_load_epi64
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h: In function 'void Eigen::internal::pstoreu(Scalar*, const Packet&) [with Scalar = int; Packet = __vector(8) long long int]':
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h:1161:31: error: '_mm512_storeu_epi32' was not declared in this scope; did you mean '_mm512_store_epi32'?
1161 | EIGEN_DEBUG_UNALIGNED_STORE _mm512_storeu_epi32(to, from);
| ^~~~~~~~~~~~~~~~~~~
| _mm512_store_epi32
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h: In function 'void Eigen::internal::pstoreu(Scalar*, const Packet&) [with Scalar = long int; Packet = Eigen::internal::eigen_packet_wrapper<__vector(8) long long int, 1>]':
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h:1165:31: error: '_mm512_storeu_epi64' was not declared in this scope; did you mean '_mm512_store_epi64'?
1165 | EIGEN_DEBUG_UNALIGNED_STORE _mm512_storeu_epi64(to, from);
| ^~~~~~~~~~~~~~~~~~~
| _mm512_store_epi64
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h: In function 'void Eigen::internal::pstoreu(Scalar*, const Packet&) [with Scalar = short int; Packet = Eigen::internal::eigen_packet_wrapper<__vector(8) long long int, 6>]':
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h:3000:3: error: '_mm512_storeu_epi32' was not declared in this scope; did you mean '_mm512_store_epi32'?
3000 | _mm512_storeu_epi32(out, x);
| ^~~~~~~~~~~~~~~~~~~
| _mm512_store_epi32
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h: In function 'void Eigen::internal::pstoreu(Scalar*, const Packet&) [with Scalar = short int; Packet = Eigen::internal::eigen_packet_wrapper<__vector(4) long long int, 6>]':
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h:3006:3: error: '_mm256_storeu_epi32' was not declared in this scope; did you mean '_mm256_store_epi64'?
3006 | _mm256_storeu_epi32(out, x);
| ^~~~~~~~~~~~~~~~~~~
| _mm256_store_epi64
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h: In function 'void Eigen::internal::pstoreu(Scalar*, const Packet&) [with Scalar = short int; Packet = Eigen::internal::eigen_packet_wrapper<__vector(2) long long int, 6>]':
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h:3012:3: error: '_mm_storeu_epi32' was not declared in this scope; did you mean '_mm_store_epi64'?
3012 | _mm_storeu_epi32(out, x);
| ^~~~~~~~~~~~~~~~
| _mm_store_epi64
```
#### Clang Example
With clang < 10.0.0 and flags `-mavx512f -mavx512vl -mfma`
```cpp
#include <Eigen/Dense>
int main() {
using mat_t = Eigen::Matrix<unsigned int, -1, -1>;
mat_t A = mat_t::Random(10, 10);
Eigen::Matrix<double, -1, -1> B = A.template cast<double>();
return 0;
}
```
https://godbolt.org/z/fsqhsKMWc
This produces the error
```clang++
In file included from <source>:1:
In file included from /opt/compiler-explorer/libs/eigen/vtrunk/Eigen/Dense:1:
In file included from /opt/compiler-explorer/libs/eigen/vtrunk/Eigen/Core:222:
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h:1336:10: error: use of undeclared identifier '_mm512_cvtsi512_si32'; did you mean '_mm512_castsi512_si128'?
return _mm512_cvtsi512_si32(a);
^
/cefs/f0/f03e5f34867580d0ae719b6e_consolidated/compilers_c++_clang_9.0.1/lib/clang/9.0.1/include/avx512fintrin.h:491:1: note: '_mm512_castsi512_si128' declared here
_mm512_castsi512_si128 (__m512i __A)
^
In file included from <source>:1:
In file included from /opt/compiler-explorer/libs/eigen/vtrunk/Eigen/Dense:1:
In file included from /opt/compiler-explorer/libs/eigen/vtrunk/Eigen/Core:222:
/opt/compiler-explorer/libs/eigen/vtrunk/Eigen/src/Core/arch/AVX512/PacketMath.h:1336:10: error: cannot initialize return object of type 'int' with an rvalue of type '__m128i' (vector of 2 'long long' values)
return _mm512_cvtsi512_si32(a);
^~~~~~~~~~~~~~~~~~~~~~~
2 errors generated.
Compiler returned: 1
```
### Steps to reproduce the issue
See above godbolt
### What is the current *bug* behavior?
Compiler error
### What is the expected *correct* behavior?
Program compiles
### Relevant logs
See godbolt
### Anything else that might help
I think this is very related to https://gitlab.com/libeigen/eigen/-/issues/2045
For Stan you can see the failing Jenkins build [here](https://jenkins.flatironinstitute.org/blue/organizations/jenkins/Stan%2FMath/detail/PR-3271/13/pipeline). Locally I'm seeing the following set of intrinsics that are failing with gcc 7.8.0
```
_mm256_set_m128d
_mm512_loadu_epi32
_mm512_loadu_epi64
_mm512_storeu_epi32
_mm512_storeu_epi64
_mm256_set_m128i
_mm256_set_m128d
_mm256_set_m128
_mm512_cmpneq_ps_mask
```
On clang < 9.0
```cpp
_mm512_cvtsi512_si32
```
What is the current minimum supported compiler version for Eigen?
issue
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